How to troubleshoot custom content elements in Composer
Summary
How can I debug custom content elements built to use in Composer?
Procedure
Reproduce the issue in the browser (submit, save, etc...)
Check out the network request made by the feature
Look in the network tab for the call made by the custom element
If the call is made to a PageBuilder content source (includes .arcpublishing.com),
If you CORS error for the network request, open an ACS ticket
Debug the content source to make sure Arc is working as expected
If the URL is external, the you should investigate it on you side